At night, Jiayuguan's high-rise hotels and neon lights rise from the Gobi Desert like a Chinese Las Vegas.

The reality on the ground is rather different, however. The broad, clean streets are empty by 10pm and the antics of a Tibetan dance troupe are about as wild as the nightlife gets.

Jiayuguan is perched on the far western end of the Great Wall in Gansu province, a point where for centuries China ended and the rest of the world began. It's an oasis not only of trees, shade and water, but also of tourist money, thanks mainly to the spectacular 14th-century fort that shares the city's name.

Built in the "throat" of the Silk Road - the narrow corridor between the 5,000-metre peaks of the Qilian and the dry, rocky Mazong mountain ranges - for many years this was traders' and travellers' only gateway into to China.

If allowed to pass, the visitors behind the Wall were safe from the marauding mobs of Mongols in the north. This wasn't exactly the intended purpose of the Wall we see today - trading activity on the Silk Road declined under the Ming Dynasty (1368-1644), well-known for its suspicion of outsiders. But through the Hexi Corridor, the remains of the world's greatest wall and the world's greatest road snake side by side, forced together by the parallel mountain ranges. Touring by bicycle is an exhilarating way to absorb their combined and sometimes contradictory influences.

Gateway to China

With its 11m walls, watchtowers, battlements and a single giant door, Jiayuguan stands as a monument to Ming China's isolation from the outside world. Approaching it from the west, the structure is indeed imposing. One can imagine an awestruck long-distance trader catching sight of it and simply turning back into the desert with his camels.

But Jiayuguan is not quite the end of the Wall. It struggles in its last 8 kilometres, barely distinguishable from the surrounding desert as it winds towards the Beida River. While emptiness and disappointment often prevail at China's over-hyped tourist attractions, the end of the Great Wall is truly the opposite.

Based on a taxi driver's suggestion to not bother with it, I was expecting a broken-up mound of dirt and a token sign. Both are there, but so is a small hole in the ground with a set of stairs leading down. Walk down, and suddenly you're on a glass-floored balcony hanging off a 90-degree cliff face, with a 50m-deep canyon below, the end of the Wall above, and the slopes of the towering Qilian Mountains opposite.

Though sections just north of Jiayuguan have been convincingly rebuilt, as the Wall turns back east it is once again rapidly disappearing. In parts only the remnants of watchtowers remain. Elsewhere, it's decaying irregularly, leaving behind graceful, windblown shapes. In some places the Wall has vanished without a trace. The people and their fields of onions and donkeys are its only legacy.

According to the Great Wall Museum in Jiayuguan, much of the arable land here has been painstakingly reclaimed from the desert. During the Ming Dynasty a million soldiers guarded the length of the Wall, but to feed them the government had to assign 70 percent of the soldiers' time to cultivating nearby wasteland, resulting in narrow strips of fields clinging to the Wall.

It was a classic man-versus-nature battle. The truce lines between desert and field are so stark that you can literally have one foot in the desert and the other in a green field. The only trees are tall poplars planted in neat, compact rows between the fields - walls built to keep the desert out.

It's true that the best accommodation on offer in the Chinese countryside is often a bed with no mattress on a concrete floor in what looks and feels like a prison cell. And a tiny village only 6km north of Jiuquan City on the Jiujin Highway isn't the kind of place you should expect there to be anywhere to stay at all. But at the end of Yinda's dusty main street, behind the local school, sits a stunning chalet in the middle of a willow-ringed lake. A touch of bargaining, and a brand new (if slightly basic) double room comes in at under RMB45 (US$6.50, €4). Across the bridge, the hotel bar and courtyard serves dinners, drinks, snacks and a long list of Chinese breakfast choices.

Just 30km east of Jiuquan awaits a surreal confluence of worlds. Where the fields end and the Gobi Desert takes over lies the pristine-looking Yuanyang Lake Reservoir that looks like it might have been taken from the interior of Africa, except for the imposing, bald Afghanistan-style mountains leading down to the western shore. To the south, the view stretches along the lake shore, across green fields to the snow-capped Qilian peaks, while across the road immediately to the east, a pockmarked plateau of dead grey pebbles. Despite its flawless façade, however, Jiuquan's industry and population on the Beida River upstream have made the lake's water so polluted it is now unsuitable even for irrigation.

Biking the Wall

Following the Wall across this desert on a bicycle is an exhilarating two-day adventure. The Wall here was built over 2,000 years ago by the Han Dynasty (206 BCE-220 CE), which actively sought to protect the Silk Road with its walls. This combination of Road and Wall helped the Han become one of the golden ages of Chinese civilisation.

The sand dunes provide perfect camping spots and several oasis villages punctuate the 90km of desert. Just don't go via Jinta, 10km north of Yuanyang Lake - despite its tourist-friendly appearance, it's off-limits to foreigners, the police told me as they escorted me away.

The resting Buddha

Back on today's major transport route awaits the city of Zhangye, 250km east of Jiayuguan. Two millennia ago it was one of the most important frontier garrisons in the Han's quest for control of the Hexi Corridor. Once this was achieved, Zhangye quickly became a rich trading centre. It was at this time, with the Great Wall protecting the Silk Road, that Buddhism arrived in China.

While the Silk Road's path is replete with ancient Buddhist marvels, few can rival Zhangye's giant sleeping Buddha in either magnitude or maintenance. At 34.5m long, it claims to be the "world's largest indoor sleeping Buddha", and remains in superb shape despite being made of wood over 900 years ago. Be sure to leave time to explore the rest of the temple grounds, as the Buddhist artwork around the smaller temples is truly mind-boggling.

The name Zhangye, an abbreviation of zhang guo bi ye, yi tong xi cheng ("to extend the arm of the country, through to the western realm"), is reflected in the many minority groups populating the region, including the Muslim Uighur and Hui groups. Like Buddhism before it, Islam came to China along the Silk Road. But although the Mongol Yuan Dynasty (1280-1368) had encouraged Muslim immigration to China, Muslim generals figured prominently in the early Ming Dynasty that replaced it, helping keep the Mongols outside the Wall. Centuries later, as European countries made inroads into China, they knew and feared the "Mohammedan" soldiers of Gansu as especially fierce, anti-foreign Chinese patriots.

Unlike the Turkic Uighurs, Islam is the Hui group's defining characteristic. They are Chinese in almost every way that does not contradict Islam: They don't drink alcohol, but they speak Mandarin; they don't eat pork, but they cook most Chinese dishes. Hui restaurants are common throughout Gansu, identifiable by their green signs with crescents and splashes of Arabic script. Their barbecued meat kebabs, Gansu-style chao mian (stir-fried noodles) and flat breads are not to be missed.

Remains of the Wall

There's no Great Wall left to speak of around Zhangye but 65km further east, just outside Shandan County, it's astonishingly complete. Set among scrubby grassland carved through by dry canyons, the original rammed-earth Wall still stands 5-7m high and stretches continuously as far as the eye can see.

Well, almost: The only breaks are where local shepherds have cut gaps to bring their flocks through. It's so solid they have even burrowed out small rooms in the wall, from which they can watch their flocks, sheltered from the strong winds that whip across the plains.

The winds make the Wall's condition here all the more amazing, but villagers say people, not nature, are the biggest cause of the Wall's destruction. Perhaps it's the Shandan Wall's usefulness as a windbreak that has saved it from the ravages of human activity.

The Shandan Great Wall runs parallel to and only about 1km from the Zhangye-Wuwei freeway. Predictably bicycles, three-wheeled trucks, motorbikes and various other classes of "agricultural vehicles" are banned, but freeways in China usually have small roads running alongside for the slower forms of transport. But here the road suddenly peters out, leaving the cyclist a choice between the emergency lane of the freeway or back to the bus station in Shandan.

In the 30km after Shandan, the freeway and the Wall gain about 1,000m in altitude on the way to Yongchang County, home of the reputed (but disputed) descendents of a group of Roman soldiers captured on the Silk Road more than two millennia ago.

And after Wuwei, the next city, the Silk Road and the Great Wall split for good. The Wall continues east towards Ningxia, while the Road's path banks south towards Lanzhou, Gansu's provincial capital. But the cities, monuments, villages and mountains of the Hexi Corridor have ensured that the two have remained part allies - and part opponents - in shaping China's past.